The invention concerns a method for increasing the spontaneity of an electrohydraulically controlled automatic transmission in which a gear shift is carried out while a first clutch opens and a second clutch closes.
In automatic transmissions, the gear shifts can be carried out as overlapping gear shifts while a first clutch opens and a second clutch closes. The pressure curve of the clutches taking part in the gear shift is determined via electromagnetic actuators by an electronic transmission control. Such control and regulation method is known, for ex., from DE-OS 42 40 621.
Gear shifts of the automatic transmission are usually triggered when a desired performance presettable by the driver, e.g. throttle valve position, an upshift or downshift characteristic line of a shift characteristic field, is exceeded. In addition to said gear shifts triggered by means of the accelerator pedal, the driver also has the possibility at any desired time to trigger manual gear shift. DE-OS 43 11 886, e.g. thus shows a device by which a driver can trigger gear shifts by means of a selector lever having a manual gate or switching levers on the steering wheel. In the practice, the problem arises, particularly in downshift with a subsequent upshift, that a sharp divergence appears between the driver's desired performance and corresponding acceleration capacity in relation to the adjusted gear of the automatic transmission. A typical example of this is when a driver intends to overtake another vehicle. At the start of the overtaking operation he will actuate the accelerator pedal so that the automatic transmission carries out a downshift. If the driver notices that he must interrupt the overtaking operation in view of the traffic coming from the opposite direction, he will release the accelerator pedal. The automatic transmission will first carry out a complete downshift, a retention time then elapses and only then does the upshift take place. This time lapse between the driver's desired performance and reaction thereto of the automatic transmission will be felt as disagreeable by a driver.
The problem on which the invention is based now consists in improving the spontaneity of an automatic transmission.